The invention relates to a device for holding and/or creating a dental prosthesis, with a metal main body intended to be at least partially anchored in a bone and having a hole, and with a metal bolt which can be secured in the hole of the main body and which protrudes into a hole of a ceramic body and is rigidly connected thereto. The dental prosthesis can be, for example, a single artificial tooth, a bridge, or a prosthesis comprising a plurality of teeth.
Many known devices for creating a dental prosthesis comprise an implant which can be implanted into a bone and is made of titanium or a titanium alloy, and an abutment element which lies on the implant in the area of the soft tissue and/or slightly above the latter. However, an implant with a metal surface contiguous with the soft tissue sometimes causes irritations and inflammation of the soft tissue. The abutment element is sometimes made of gold or a gold alloy. If parts with outer surfaces made from different metal materials come into contact with each other in the area of the soft tissue or in the oral cavity, these parts, together with the acid-containing saliva and/or the tissue fluid, can act as a galvanic element, generate an electric current and cause additional irritations. Known devices often have a conical or cylindrical pier made of titanium or titanium alloy which projects from the implant and on which a crown or another abutment element is mounted. Such metal piers have the disadvantage that they are poorly adaptable to individual shapes in the mouth of a patient. One reason for this is that, for example when grinding such a part, unwanted metal particles arise and get into the patient""s mouth. If a porcelain crown is applied to a metal pier, the pier often also causes an esthetically unwelcome matt hue of the porcelain crown.
To avoid irritations of the soft tissue, it is known to provide devices with a ceramic body in the area of the soft tissue. For example, U.S. Pat. No. 5,310,343 discloses devices with a metal main body and with a metal bolt, which can be screwed together with the latter. The main body and the bolt have, in cross section, portions surrounded by ceramic material. However, at its end protruding from the main body, the bolt has an open hexagonal hole, i.e. one not covered by ceramic material If, after the device has been inserted into the mouth of a patient, an impression of the device and of the teeth adjacent to it is made, the hexagonal hole should however be temporarily sealed for impression-taking. This makes impression-taking more time-consuming and more complicated. Moreover, it would often be desirable for the ceramic material secured on the bolt to be ground also in the central area in order to permit optimum adaptation of the shape to the individual situation. However, because of the hexagonal hole, this too is not possible. In these known devices, a metal flange of the bolt is present between the ceramic material arranged on the main body and the ceramic material arranged on the bolt. This metal flange can come into contact with the soft tissue and may be visible from outside and thus impair the effects, which are sought using the ceramic material. Moreover, the ceramic material cannot be ground continuously from the level of the bolt to the level of the main body without also grinding the metal flange. No metal parts should be ground inside the mouth of a patient, however, since metal chips then get into the patient""s mouth. In the devices known from U.S. Pat. No. 5,310,343, the hole of the main body and the bolt have conical portions fitting into each other. Moreover, the main body and the ceramic material arranged on it together form a plane annular surface toward which a plane annular face of the flange is directed when the device is assembled. Because of the manufacturing inaccuracies, however, either only the conical portions of the main body hole and bolt or only said plane annular surfaces can lie on each other free of gaps. If the conical portions do not lie on each other free of gaps, the upper bolt portion, the ceramic material arranged thereon, and an abutment mounted on the latter can execute micro movements directed transversely with respect to the axis of the main body. If, by contrast, a gap is present between the annular surfaces, microorganisms can penetrate into this gap. Both said micro movements and penetrating microorganisms can jeopardize the permanent securing of the device in the mouth of a patient.
The object of them invention is to avoid disadvantages of the known devices and in particular to make available a device which, after insertion into a mouth of a patient, permits rapid and simple impression-taking and casting, and whose parts protruding from the bone can, if so desired, be ground within the patient""s mouth without any problem. In addition, the device is preferably intended to ensure that no microorganisms can penetrate between the main bodies and the bolt and the ceramic body secured on the latter, and that the ceramic body secured on the bolt is connected to the metal main body in a very stable manner so that, even under the effect of substantial forces acting approximately transversely with respect to the axis of the main body, this ceramic body as far as possible executes no movements relative to the main body. In addition, for creating a dental prosthesis in the mouth of a patient, the device is intended to be able to be assembled from as few separate parts as possible.
This object is achieved by means of a device for holding and/or creating a dental prosthesis including a metal main body adapted to be at least partially anchored in a bone with a hole, a metal bolt which is secured in the hole of the main body, and a ceramic body with a hole to which the metal bolt is rigidly connected wherein the hole of the ceramic body is a blind hole in that it has an end directed away from the main body and the end is closed off by ceramic material of the ceramic body.
Advantageous embodiments of the device will be evident from the dependent claims.
The device design according to the invention permits, after insertion of the device into a patient""s mouth, rapid and simple impression-taking, i.e. casting of those device parts protruding from the bone and passing through the soft tissue. In particular, it is not necessary, for impression-taking, to temporarily cover any hole of the ceramic body secured on the bolt and/or of the bolt itself. In addition, if necessary, the central portion of the ceramic body secured on the bolt, covering the bolt end protruding from the main body, can be ground in the patient""s mouth area.
The device moreover permits a rigid, stable, permanent and indirect connection of the metal main body to the ceramic body secured on the bolt. In addition, in order to create a dental prosthesis in the mouth of a patient, a dentist has to assemble only a small number of separate parts.
In an advantageous embodiment of the device, the main body has an axial portion surrounded in cross section by ceramic material. This ceramic material and the ceramic body secured on the bolt consist, for example, of originally separate ceramic bodies. The ceramic body secured on the main body, and the ceramic body secured on the bolt, are connected directly to the main body or bolt, respectively, by means of a binder. Depending on the design of the parts to be connected to each other, the binder can consist of a thinly fluid adhesive to be applied in a thin layer, or of a relatively viscous adhesive or cement, which is suitable for filling at least one relatively large interspace. When joining the parts together, the adhesive and/or cement can set at normal room temperature, for example, or can be heated to allow setting. Instead of being joined by an adhesive or cement, the or each ceramic body may possibly be connected to the metal main body or bolt by means of a hard solder connection. In this case, the binder then consists of a hard solder which is temporarily heated and melted when connecting the ceramic body to the metal main body or bolt. The binder must in all cases be biocompatible, nontoxic, and well tolerated by the bones and soft tissues of patients. The ceramic body can furthermore form a press-fit together with the main body or the bolt and, instead of using a binder, or in addition to such a binder, can be connected to the main body or bolt by a press-fit connection.
The or each ceramic body can be shaped separatelyxe2x80x94i.e. separate from the main body and relevant boltxe2x80x94for example using a plastically deformable mass which comprises particles and is more or less easily flowing, and with the aid of a casting mold or the like, in such a way that it is at least substantially rotationally symmetrical with respect to an axis. Before being connected to a main body or bolt, the shaped body is then heated and sintered in the usual way. If two ceramic bodies are present, one or either of them, when used to create a dental prosthesis, can if necessary be ground further in places in the mouth of a patient by a dentist and thereby individually shaped on production of an abutment element or superstructre.
The ceramic material, or at least part thereof, secured preferably directly on the main body can furthermore form a ceramic covering connected to the main body in a nonreleasable manner. The ceramic covering can be applied, for example sprayed, nonreleasably onto an area of the metal main body. This covering can consist of a thin layer whose thickness is for example at most 100 xcexcm only, and for example approximately 50 xcexcm.
The metal main body, and the metal bolt secured in the hole of the main body, can be made of titanium or a titanium alloy, for example. The or each ceramic body and/or the ceramic covering preferably consists of oxide ceramic, for example aluminum oxide and/or magnesium oxide and/or zirconium oxide, and is preferably electrically insulating.